Characterization of feed efficiency traits and relationships with feeding behavior and ultrasound carcass traits in growing bulls

Abstract

The objectives of this study were to characterize feed efficiency traits and to examine phenotypic correlations between performance and feeding behavior traits, and ultrasound measurements of carcass composition in growing bulls. Individual DMI and feeding behavior traits were measured in Angus bulls (n=341; initial BW=371.1+/-50.8 kg) fed a corn silage-based diet (ME=2.77 Mcal/kg of DM) for 84 d in trials 1 and 2 and for 70 d in trials 3 and 4 by using a GrowSafe feeding system. Meal duration (min/d) and meal frequency (events/d) were calculated for each bull from feeding behavior recorded by the GrowSafe system. Ultrasound measures of carcass 12th-rib fat thickness (BF) and LM area (LMA) were obtained at the start and end of each trial. Residual feed intake (RFIp) was computed from the linear regression of DMI on ADG and midtest BW(0.75) (metabolic BW, MBW), with trial, trial by ADG, and trial by midtest BW(0.75) as random effects (base model). Overall ADG, DMI, and RFIp were 1.44 (SD=0.29), 9.46 (SD=1.31), and 0.00 (SD=0.78) kg/d, respectively. Stepwise regression analysis revealed that inclusion of BW gain in BF and LMA in the base model increased R(2) (0.76 vs. 0.78) and accounted for 9% of the variation in DMI not explained by MBW and ADG (RFIp). Residual feed intake and carcass-adjusted residual feed intake (RFIc) were moderately correlated with DMI (0.60 and 0.55, respectively) and feed conversion ratio (FCR; 0.49 and 0.45, respectively), and strongly correlated with partial efficiency of growth (PEG; -0.84 and -0.78, respectively), but not with ADG or MBW. Gain in BF was weakly correlated with RFIp (0.30), FCR (-0.15), and PEG (-0.11), but not with RFIc. Gain in LMA was weakly correlated with RFIp (0.17) and FCR (-0.19), but not with PEG or RFIc. The Spearman rank correlation between RFIp and RFIc was high (0.91). Meal duration (0.41), head-down duration (0.38), and meal frequency (0.26) were correlated with RFIp and accounted for 35% of the variation in DMI not explained by MBW, ADG, and ultrasound traits (RFIc). These results suggest that adjusting residual feed intake for carcass composition will facilitate selection to reduce feed intake in cattle without affecting rate or composition of gain.

Assessing feed efficiency in beef steers through feeding behavior, infrared thermography and glucocorticoids

“…As a result of the correlations of MS and ER with DMI, a corresponding response was also found for the other productive performance traits. Differently from our results, Lancaster et al (2005) did not find significant correlations between F : G and ER. The correlation between ADG and TF was comparable to the findings of Schwartzkopf-Genwein et al (2002) and Lancaster et al (2005).…”

“…Differently from our results, Lancaster et al (2005) did not find significant correlations between F : G and ER. The correlation between ADG and TF was comparable to the findings of Schwartzkopf-Genwein et al (2002) and Lancaster et al (2005). In relation to RFI (Tables 3 and 4), steers that consumed larger meals (MS) and in a shorter period of time (ER) had a less desirable RFI, which was also found by Gomez et al 2007, but not by Lancaster et al (2005) and Golden et al (2008).…”

“…The correlation between ADG and TF was comparable to the findings of Schwartzkopf-Genwein et al (2002) and Lancaster et al (2005). In relation to RFI (Tables 3 and 4), steers that consumed larger meals (MS) and in a shorter period of time (ER) had a less desirable RFI, which was also found by Gomez et al 2007, but not by Lancaster et al (2005) and Golden et al (2008). The relationship between ER and RFI is supported by the association between RFI and basal energy requirements (Richardson et al, 2001;Castro Bulle et al, 2007) and the findings from Adam et al (1984), where ER was a key factor in determining the energy cost of eating in cattle.…”

“…The relationship between ER and RFI is supported by the association between RFI and basal energy requirements (Richardson et al, 2001;Castro Bulle et al, 2007) and the findings from Adam et al (1984), where ER was a key factor in determining the energy cost of eating in cattle. Time spent at the feeder was correlated with RFI in our study and also in the study conducted by Lancaster et al (2005). Additionally, Nkrumah et al (2006) observed that high-RFI steers spent 50% more time feeding in comparison to low-RFI steers.…”

“…These differences are probably not only due to the experimental differences but also to the diversity of definitions for meal across these studies. The positive correlation of VF with RFI was also found by Lancaster et al (2005) in growing beef bulls. VF was different across the RFI-groups (Table 4), with low-RFI steers having fewer VF, which is similar to the pattern observed by Nkrumah et al (2006).…”